136 THE BOOK OF A NATURALIST 
tongue,” says Lacepede in his Natural History of 
Serpents, “is to catch insects, which it catches by 
means of its double tongue.” This notion about 
the use of the double tongue is quite common 
among the older ophiologists, and, along with it, 
the belief that snakes prey chiefly on insects. And 
here I cannot resist the temptation to quote a few 
more words touching on this point from Lacepede 
—a very perfect example of the teleological spirit 
in science which flourished a century ago, and made 
things easy for the naturalist. ‘We are not,” he 
says, ‘‘to be amazed at the vast number of serpents, 
both species and individuals, which inhabit the 
intertropical countries. There they find the degree 
of warmth which seems congenial to their natures, 
and the smaller species find abundance of insects to 
serve them for food. In those torrid regions, where 
Nature has produced an infinite multitude of 
insects and worms, she has likewise produced the 
greatest number of serpents to destroy the worms 
and insects; which otherwise would multiply so 
exceedingly as to destroy all vegetable productions, 
and to reduce the most fertile regions of the earth 
into barren deserts, inaccessible to man and animals; 
nay, even these noxious and troublesome insects 
would be finally obliged to destroy each other, and 
nothing would remain but their mangled limbs.” 
Here the French naturalist pauses, aghast at the 
frightful picture of desolation he has himself con- 
jured up. 
When enumerating the uses to which a serpent 
